The Sages instituted the public reading of four Torah passages (parshiyot) in addition to the weekly Torah portion: Parashat Shekalim, Parashat Zakhor, Parashat Para, and Parashat Ha-ĥodesh. We read each of the latter three parshiyot on a Shabbat during the month of Adar, while Parashat Shekalim is usually read on the Shabbat before Adar begins.
On these Shabbatot, we take out two Torah scrolls from the ark. First, we read the weekly parsha from the first scroll, dividing it into seven aliyot as on any other Shabbat. Then, we read the special parsha as maftir (the concluding aliya that precedes the haftara) from the second scroll. Since the haftara, which is a section from the Prophets, must relate to the content of the maftir, the haftarot of these weeks all deal with themes connected to the special parsha that was read from the second scroll, not to the weekly portion that was read from the first.
The first of the four parshiyot is Parashat Shekalim (Shemot 28:9-15). This parsha was instituted to remind every Jew to contribute the yearly half-shekel, which was used to purchase communal offerings. Since it was necessary to begin purchasing the offerings with the new funds in Nisan, the Sages instituted the reading of Parashat Shekalim a month earlier, to remind everyone to make his donation. Even though the Temple is in ruins today, and we do not have the privilege of bringing sacrifices, we read Parashat Shekalim in commemoration of the Temple (see mb 685:1, Mikra’ei Kodesh §3).
The second parsha is Parashat Zakhor (Devarim 25:17-19). This reading fulfills the Torah commandment to remember what the Amalekites did to us. The Sages ordained that we read this parsha before Purim in order to juxtapose the mitzva of remembering Amalek to Purim, when we celebrate the fulfillment of that mitzva through the elimination of Haman, who was a descendant of Amalek.
The third parsha is Parashat Para (Bamidbar 19:1-22), which instructs one how to purify himself from ritual impurity, so that he may enter the Temple and bring offerings. The Sages instituted that it be read as the month of Nisan approaches, so that one can prepare and purify himself for the upcoming Pesaĥ offering. Even though we do not bring this offering nowadays, we read Parashat Para in commemoration of the Temple.
The fourth parsha is Parashat Ha-ĥodesh (Shemot 12:1-20), which mentions the sanctification of the new moon and the mitzvot of Pesaĥ. The reading of his parsha was instituted for just before the beginning of Nisan, because Nisan is the first month of the year in the Torah’s accounting and because it alerts us to start preparing for Pesaĥ and all its mitzvot.
When Rosh Ĥodesh Adar or Rosh Ĥodesh Nisan coincides with Shabbat, we remove three Torah scrolls from the ark. We read the weekly portion from the first scroll, the section that deals with Rosh Ĥodesh (Bamidbar 28:9-15) from the second scroll, and the special parsha – Parashat Shekalim on Rosh Ĥodesh Adar and Parashat Ha-ĥodesh on Rosh Ĥodesh Nisan – from the third scroll.
According to most poskim, the mitzva of reading Parashat Zakhor is mandated by Torah law. Therefore, people are more meticulous about reading Parashat Zakhor than they are regarding all other readings, as we will explain below (14:6). Some maintain that reading Parashat Para also fulfills a Torah commandment, which is why people are customarily more meticulous with regard to that parsha as well.
. The institution of the four parshiyot chronologically precedes the institution of the weekly parsha reading. Although the reading of the Torah every Shabbat, Monday, and Thursday was instituted in the time of Moshe, the division of the Torah into 54 portions, to allow it to be read in its entirety over the course of a year, took place much later. In the time of the Amora’im, the Jewish community in Babylonia followed this practice, but the Jews of Eretz Yisrael would complete the Torah every three years instead of every year. However, the institution of the Four Parshiyot and the special readings for the holidays are mentioned already in the Mishna and the Talmud (Megilla 29a-30b).
Reading Parashat Zakhor is a Torah commandment, as we will explain below, in section 6. Some maintain that Parashat Para is also a Torah commandment, as sa 146:2, 685:7 states. Most authorities consider it a rabbinic enactment: see mb 146:13, 685:15; Kaf Ha-ĥayim 685:28. Le-khatĥila, Parashat Para is treated as stringently as Parashat Zakhor.